activities

type BillingActivities struct {
}

type CalculateActivityResult struct {
	InvoiceID   string
	TotalAmount float64
	Items       []InvoiceItem
}

type FetchDataActivityResult struct {
	CustomerData interface{}
	PlanData     interface{}
	UsageData    interface{}
}

type InvoiceItem struct {
	Description string
	Amount      float64
}